My girlfriend's girlfriend by type o negative
Trying to love two by william bell
Love in stereo by the monks
You're the two by roches
Cactus tree by joni mitchell
Don't ever call your sweetheart by his name by christine lavin (less about poly, more about semi-honest non-monogamy, but it's funny)
Torn between two lovers by mary macgregor
You and your friend by snake river conspiracy
Aaaaand, now that I took the time to type that out, I found an awesome list that mentions all of the above plus a whole lot more: http://www.aserve.com/holly/culturefaq.html
The major players. Me, 30ish bi female. Gia, girlfriend of 4+ years. Clay, boyfriend/dom. Davis, ex/friend/"it's complicated." Eddie, roommate & fwb.
The supporting cast. Eric, Gia's husband. Bee, Gia and Eric's toddler. Dexter, Gia's lover. Helen, Eric's lover. Izzy and Nikki, Clay's partners. Liam, Eddie's husband.